1. Field of the Invention
The present invention relates to an image processing apparatus, an image processing system and an image processing method which are all used in an apparatus or a system which performs an image correction process to print and output by a printer digital image data shot and obtained by, e.g., a digital still camera or the like, to a computer-readable storage medium which stores a program for executing the image processing method, and to the program itself.
2. Related Background Art
In recent years, for example, a digital still camera is popularized, whereby an image shot by the digital still camera can be easily digitized. In particular, a chance of handling and treating a photographic image (i.e., an image seen like a photograph) as digital image data increases on a personal computer. Moreover, by using various application programs (software) on the personal computer, the digital image data representing the photographic image can be easily processed and edited.
On one hand, a full-color hard copy technique rapidly develops. Particularly, in a print technique based on an ink-jet print system, a technique to reduce graininess of ink dots improves, whereby an image quality of the print output in this print technique becomes equivalent to an image quality of a silver-salt photograph. Furthermore, this print technique is widely used because it is relatively simple.
According to such a technical background as described above, it is required enabling to easily print the digital image data shot and obtained by the digital still camera. Furthermore, in regard to an image correction process to be performed in case of printing and outputting the image data, the need for an automatic image correction process in which an excellent image-corrected image can be obtained by using the application programs on the personal computer increases instead of a manual image correction process in which complicated functions are used.
Consequently, as a method of performing image processes such as the image correction process and the like in case of printing and outputting the image data so as to obtain an excellent output result, for example, a method of analyzing a scene of the shot image and then automatically performing the image correction based on the analyzed result, and other various methods are proposed.
Furthermore, for example, a method of performing so-called “density correction” which is the correction to prevent that the shot image is too bright (too thin) or too dark (too thick) when this image is printed and output is proposed. Moreover, a method of performing so-called “image correction” which is the correction to correct an inappropriate shot image including color fog, underexposure (defective lightness and/or contrast), defective saturation or the like and an image with the color balance being defective due to color fog or the like is proposed.
As a structure to perform the automatic image correction in both the method of performing “density correction” and the method of performing “image correction”, a structure which analyzes the image to be processed (also called an original image or a process-target image hereinafter) by using a histogram on which the numbers of pixels of each brightness value of a brightness signal in the original image have been accumulated and then corrects the original image on the basis of the analyzed result is applied.
Furthermore, the digital still camera side has a function to be able not only to record the shot and obtained image as the digital-image data in a storage medium such as a memory card or the like but also to record additional information representing a shooting (or photographing) condition at a time of image shooting together with the digital image data in the storage medium.
Here, it is assumed that the process-target image is shot by the digital still camera, the shot and thus obtained process-target image is analyzed, the scene of the analyzed process-target image is further analyzed, and the automatic image correction of the process-target image is performed on the basis of the analyzed result. In this case, basically, the automatic image correction is performed so that the images which are thought to be logically optimum (i.e., standard images) are printed and output respectively for all of the process-target images.
Incidentally, in such a color correction and a lightness correction, it is often the case that the image process is statistically performed by using the histogram of the image, that is, the optimum correction in all the images cannot necessarily be performed on the basis of the analysis of only the image data. In other words, more precise and strict judgment can be performed if white balance information and exposure information are used respectively for the color correction and the lightness correction.
Furthermore, unlike the manual image correction that a user manually corrects the process-target image by using the application program on the personal computer while confirming it displayed on the monitor of this computer, there is the fear in the automatic image correction that the correction to obtain a standard image is performed against user's intention at the time when obtaining the process-target image (i.e., at the time of shooting the process-target image).
For example, even if the user intentionally sets a manual mode and then shoots an image under an exposure condition to lighten or darken the image, the obtained light image is corrected to make it rather darker and the obtained dark image is corrected to make it rather lighter. That is, in this case, the image obtained in the manual mode is output as an image having appropriate lightness against user's intention. In other words, any process-target image is corrected and output as the image having the same lightness.
Furthermore, even if the user intentionally changes a white balance of the digital still camera to aim at a specific effect and then shoots an image based on the changed white balance, the shot image obtained is corrected to have an optimum color balance (i.e., not the changed white balance).